JP2003277812A - Platinum powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To synthesize platinum powder of arbitrary particle size using fine platinum powder. <P>SOLUTION: The fine platinum powder or fine platinum-compound powder which can be formed into the fine platinum powder by decomposition or reduction by heating is mixed with one or more kinds among alkali-metal compounds and alkaline-earth metal compounds. After heating treatment is applied to the resultant mixture, the alkali-metal compounds or the alkaline-earth metal compounds or the decomposition products thereof are removed to obtain the platinum powder of arbitrary particle size. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fine platinum powder, or a fine platinum compound powder which becomes a fine platinum powder when decomposed or reduced by heating and an alkali metal compound or an alkaline earth metal. The present invention relates to providing platinum powder of any particle size with good reproducibility and economically by mixing with one or more compounds and then subjecting to heat treatment.

[0002]

2. Description of the Related Art Conventionally, when a metal powder is generally obtained, a metal as a raw material of a desired metal is charged into a melting furnace in accordance with a desired quantity, heated to a temperature not lower than a melting point of the metal of the raw material, mixed and melted. It has been obtained by atomizing the mixture in air or liquid. However, the melting point of platinum is as high as 1774 ° C. in air, and in order to dissolve platinum in air, it is usually necessary to dissolve it at a high temperature of 1900 ° C. or higher, which is difficult to dissolve in air. In order to do so, it was necessary to use a large-scale apparatus such as melting in a vacuum. Further, even after melting, it is difficult to spray the melted material in vacuum into the air or water, and the manufacturing apparatus has to be large scale. Therefore, a particle having a stable particle shape could not be obtained.

[0003]

In the conventional method, when platinum powder is obtained, it is necessary to melt it at a high temperature of 1900 ° C. or higher and spray-disperse it in the air or in a liquid. Therefore, it is necessary to forcibly disperse the particles in the air or in the liquid, which requires a large-scale special device, and it is difficult to always obtain a stable platinum powder having a desired particle size. Therefore, the present invention is to provide a method capable of always obtaining a platinum powder having a desired particle shape.

[0004]

Means for Solving the Problems As a result of intensive studies on control of platinum powder, the present inventor has found that a platinum powder having a desired particle size and shape can be obtained, and completed the present invention. The present invention relates to a fine platinum powder, or a platinum compound which is decomposed by heating or reduced to become fine platinum powder, and one or more kinds of alkali metal compounds or alkaline earth metal compounds. After that, heat treatment is performed to always obtain a stable platinum powder having a desired particle shape.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The present invention relates to a fine platinum powder, a platinum compound which is decomposed by heating or becomes a fine platinum powder by reduction, and one or more of an alkali metal compound or an alkaline earth metal compound, The mixture is subjected to heat treatment.

The platinum fine powder used in the present invention includes:
Platinum black, platinum sponge, platinum oxide that is decomposed or reduced by heating to become fine platinum powder, dichlorotetraammineplatinum, dinitrodiammineplatinum and its nitrate, tetrachlorohexaammineplatinum, hexahydroxoplatinum Examples thereof include acids and nitrates thereof, organic platinum compounds such as sodium hexahydroxoplatinate, chloroplatinic acid, potassium chloroplatinate, and the like. The particle size of the platinum fine powder is not particularly limited, but a particle size of about 1 nm to 10000 nm is suitable.

Examples of alkali metal compounds used in the present invention include oxides, hydroxides, carbonates, sulfates, nitrates, chlorides and organic acid salts of Li, Na, K, Rb and Cs. Further, as the alkaline earth metal compound, B
Examples thereof include oxides, hydroxides, carbonates, sulfates, nitrates, chlorides and organic acid salts of e, Mg, Ca, Sr, Ba and Ra.

It is mixed with one or more of these alkali metal compounds and alkaline earth metal compounds.

Generally, a ball mill, an attritor, a planetary ball mill, or the like may be used as a mixing device for mixing, but when a ball mill or the like is used, the platinum fine powder may become flat or flaky. . When there is a possibility of the above, mixing may be performed with a high speed stirring device of 1000 rpm or more. Examples of the high speed stirring device of 1000 rpm or more include a super mixer and a Henschel mixer.

The mixture well mixed and dispersed by a mixer and a stirring device is heat-treated. The heat treatment is preferably performed in a non-oxygen atmosphere. Non-oxygen atmosphere means argon, nitrogen,
It is an atmosphere of hydrogen or a mixed gas of nitrogen and hydrogen. By heating in a non-oxygen atmosphere, the platinum compound is reduced to platinum fine powder.

In the process of heat treatment, the platinum fine particles cause grain growth between the metal powders in contact with each other, but the grain growth is hindered by the intervening alkali metal compound or alkaline earth metal compound. . Therefore, in order to obtain a platinum powder having a relatively small particle size, a large amount of the alkali metal compound and the alkaline earth metal compound to be mixed may be mixed.
In this way, a platinum powder having an arbitrary particle size can be obtained depending on the amounts of the alkali metal compound and the alkaline earth metal compound added. The particle size of the platinum powder is also affected by the heat treatment temperature and heat treatment time conditions. The heat treatment temperature is not limited, but generally 1,500 ° C. or lower is desirable. Although the heat treatment time is not limited, it is determined by the desired particle size of platinum.

The particle size of the platinum powder increases as the heating time is maintained at a high temperature for a long time, and conversely, the particle size of the platinum powder decreases when heated at a low temperature for a short time.

After completion of heating, the heat-treated product is put into water or an aqueous solution of nitric acid, sulfuric acid or the like to remove the alkali metal compound and the alkaline earth metal compound. Finally, it is thoroughly washed with water, filtered and dried to obtain platinum powder.

[0014]

EXAMPLES Next, the present invention will be described with reference to examples.
The present invention is not limited to the following examples.

Example 1 100 parts by weight of platinum black fine powder (particle diameter of about 100 nm) and potassium carbonate fine powder 40
0 part by weight was placed in a super mixer and thoroughly mixed and dispersed. Next, this mixture was put into a return furnace (electric furnace), heated at 1250 ° C. while flowing nitrogen gas, and then lowered to 850 ° C. and heated. Then, this heat-treated mixture was put into water, dispersed and filtered, and the filtered product was put into an aqueous nitric acid solution, further washed with water and dried to obtain a platinum powder. The obtained platinum powder had a particle size of about 1.4 μm.

Example 2 100 parts by weight of platinum black fine powder (particle diameter of about 100 nm) and potassium carbonate fine powder 10
0 part by weight was placed in a super mixer and thoroughly mixed and dispersed. Next, this mixture was placed in a return furnace (electric furnace) and heated at 1200 ° C. while flowing nitrogen gas. Then, this heat-treated mixture was put into water to disperse it, followed by filtration. The filtered product was put into an aqueous nitric acid solution, further washed with water and dried to obtain a platinum powder. The obtained platinum powder had a particle size of about 2.5 μm.

Example 3 100 parts by weight of platinum black fine powder (particle diameter of about 100 nm) and 400 parts by weight of magnesium carbonate fine powder were put in a super mixer and sufficiently mixed and dispersed. Next, after putting this mixture in a return furnace (electric furnace) and heating at 1250 ° C. while flowing nitrogen gas,
It was lowered to 50 ° C. and heated. Then, this heat-treated mixture was put into water to disperse it, followed by filtration. The filtered product was put into an aqueous nitric acid solution, further washed with water and dried to obtain a platinum powder. The obtained platinum powder had a particle size of about 1.5 μm.

Example 4 Platinum powder was obtained in the same manner as in Example 2, except that 100 parts by weight of fine potassium carbonate powder was changed to 100 parts by weight of barium carbonate. The platinum powder obtained had a particle size of about 2.3 μm.

[Example 5] Platinum powder was obtained by the same procedure as in Example 1 except that 400 parts by weight of potassium carbonate fine powder was changed to 400 parts by weight of calcium hydroxide. The platinum powder obtained had a particle size of about 1.7 μm.

[Example 6] Platinum fine powder (particle size: about 100)
(100 nm) and 400 parts by weight of calcium hydroxide fine powder were put in a super mixer and sufficiently mixed and dispersed. Next, after putting this mixture in a return furnace (electric furnace) and heating at 1200 ° C. while flowing nitrogen gas and hydrogen gas,
The mixture was put into water, dispersed and filtered, the filtered product was put into a nitric acid aqueous solution, further washed with water, filtered, and dried to obtain a platinum powder. The obtained platinum powder has a particle size of about 1.
It was 8 μm.

Example 7 Platinum oxide (particle size: about 100 n
m) 100 parts by weight and 500 parts by weight of potassium carbonate fine powder were put into a super mixer and sufficiently mixed and dispersed. Next, this mixture is put into a return furnace (electric furnace) and heated at 1200 ° C. while flowing nitrogen gas and hydrogen gas, and then the mixture is put into water, dispersed and filtered, and the filtered product is nitric acid. It was put into an aqueous solution, further washed with water, filtered and dried to obtain a platinum powder. The obtained platinum powder has a particle size of about 1.8 μm.
Met.

[0022]

According to the present invention, when synthesizing platinum powder, it becomes possible to synthesize platinum powder having an arbitrary particle size at a relatively low temperature. Further, the platinum powder can be stably synthesized with a particle size depending on the addition amount of the alkali metal compound or the alkaline earth metal compound and the heating temperature. Furthermore, the platinum powder is
It is possible to synthesize particles having a substantially uniform particle size.

Claims (4)

[Claims] 1. A platinum powder obtained by mixing fine platinum powder with one or more of an alkali metal compound or an alkaline earth metal compound, and then heat-treating the mixture. 2. A fine powder of a platinum compound which is decomposed by heating or reduced into a fine platinum powder is mixed with one or more kinds of an alkali metal compound or an alkaline earth metal compound. Then, a platinum powder obtained by heating the mixture. 3. Platinum fine powder, or a fine powder of a platinum compound which becomes a fine platinum powder when decomposed or reduced by heating, and one or more of an alkali metal compound or an alkaline earth metal compound. Platinum-rhodium alloy fine powder obtained by heating the mixture after mixing with the above. 4. Platinum fine powder, or a fine powder of a platinum compound which becomes a fine platinum powder when decomposed or reduced by heating, and one of an alkali metal compound or an alkaline earth metal compound, or 1000 rp and above
A method for producing platinum powder, which comprises mixing with a high-speed stirring device of m or more and then heat-treating and then removing an alkali metal compound or an alkaline earth metal compound or a decomposed product of the alkali metal compound or an alkaline earth metal compound.